Conventionally, it is proposed to detect an object existing in the surroundings of a vehicle, such as a preceding vehicle, a pedestrian or obstacles by using a distance measuring sensor such as an ultrasonic sensor mounted on the vehicle, and to perform various processes to improve a running safety of the vehicle such as actuating a braking device or notifying a driver based on an object detection result.
In a vehicle width direction, which is a direction perpendicular to a traveling direction of the vehicle, there is a small possibility that the vehicle and the object will come in contact if the object is not present in a range of the vehicle width.
However, when measuring only a distance between the vehicle and the object, the position of the object in the vehicle width direction cannot be detected, and it may be determined that there is a possibility that the vehicle will contact the object even if no object exists in the vehicle width, thus an actuation of the braking device or notification to the driver takes place.
In this respect, as for detecting the position of the object positioned in front of the vehicle in the vehicle width direction, there is an object detecting apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2014-89077.
In the object detecting apparatus according to the Publication No. 2014-89077, two distance measuring sensors are mounted in the vehicle, and a position of the object in the vehicle width direction is calculated by using the principle of triangulation.
Then, if the position of the object in the vehicle width direction is within the vehicle width, it is determined that there is a risk of the vehicle contacting with the object, and if the position of the object in the vehicle width direction is not within the vehicle width, it is determined that there is no risk of the vehicle contacting with the object.
By executing this process, the object detecting apparatus according to the Publication No. 2014-89077 can suppress the braking device from operating when no object exists within the vehicle width.
In the object detecting apparatus disclosed in the Publication No. 2014-89077, a number of detectable objects in a single object detecting opportunity is limited to one.
If a plurality of objects is present in front of the vehicle, only an object present at a position closest to the vehicle is detected, and another object that is present farther away from the closest object cannot be detected.
At this time, if the object that exists in the nearest position is not present within the vehicle width, and the distant object is present within the range of the vehicle width, there is a risk that the braking device may not be operated.
In this respect, in addition to a reflected wave of the object positioned in the most vicinity of the vehicle, a reflected wave of the other object present in a farther position is received as a second wave, and an object may be detected by using the second wave also.
However, depending on the position of the object and a shape of the object relative to the vehicle, it is believed that a repetition of reflection between the same object, or so-called multiple reflection occurs.
In other words, when detecting an object by using the second wave, the second wave may be reflected several times by a first object.
At this time, when calculating the position of the object by using the second wave, a position of a second object that does not actually exist may be calculated incorrectly, and a braking control, etc. to avoid contacting with an object that does not actually exist may be performed.
The same situation may occur even when a reflected wave of a third wave and after is used in addition to the second wave for detecting the object.